Multilayer films that have alternating layers of polymeric materials are used in a variety of different industries and applications. In the packaging industry, for instance, multilayer films are used to package foods, beverages, and consumer products, among other items. The different layers of the multilayer film can act as a barrier to prevent the ingress and egress of moisture, oxygen, and other gases that can reduce the shelf life of the packaged product. As another example, multilayer films are used as optical films in computer monitors, windows, and other optical systems. The different layers of the multilayer film can have different optical properties, such as different indices of refraction, which control light transmission and display through the film.
The optical and physical properties of a multilayer film typically depends on a number of variables such as the type of polymeric materials used for the individual layers of the film, the overall number of individual layers in the film, and thickness of each individual layer in the film. For example, some multilayer films currently produced have dozens or even hundreds of individual layers, where each layer is only a few microns thick. Properly controlling the formation of these individual layers during the film manufacturing process can help ensure that the resultant multilayer film has the desired optical and/or physical properties.
A layer multiplication device, which is often referred to as a layer multiplier, is a device used during the film manufacturing process to multiply the number of individual layers in a film. The layer multiplication device may take a film that has two layers of different material stacked one on top of another, for example in an A-B configuration, and replicate the layer structure, for example, to produce a film that has an A-B-A-B layer configuration. The process of dividing and recombining layers within the layer multiplication device can generate shear forces and cause pressure drop across the device. If great enough, these shear forces can damage the physical structure of the multilayer film during manufacture and/or cause different layers of the film to blend together, preventing the formation of a well-defined multilayer film stack.